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Quick Question on RMS

Discussion in 'Recording' started by iamfrobs, Jan 13, 2009.

  1. iamfrobs

    iamfrobs Guest

    Hey RO,
    Quick question, from what I can gather from the internets, RMS is an average of the volume. I know it means Root-Mean-Square, but can anyone elaborate? I am using Reaper, and it comes up in the output track.

    thanks
     
  2. Cucco

    Cucco Distinguished Member

    Essentially, it helps to guage your average headroom in the track. It is (oversimplification ahead...) an average of the peaks and minimums within the track. When factored in "real time" it typically averages over a pre-set amount of samples - usually enough to capture a few seconds of audio. When factored over the entire track, it's an average of all of the levels.

    It's quasi-useful information at best - don't get caught up in what it says. If your recordings are coming out at -8dBFS RMS though, you may be pushing them too much.

    Cheers-
    J.
     
  3. iamfrobs

    iamfrobs Guest

    Thanks J.
     
  4. RemyRAD

    RemyRAD Guest

    Also the RMS compressors more closely mimic optical units in their functioning. Like optical units, most RMS units don't include adjustable attack & release controls except on the very high and units.

    It's quite different sounding from peak detection as found in Universal Audio/UREI 1176/1178 style units.

    So when I'm recording and/or mixing and I'm not by getting when I want on whatever it is I want? I'll switch from a RMS to a peak detector unit. Or, vice versa. The sound that they impart are quite different from one another. There is no real right or wrong ways to use them. But as you have probably surmised, peak detector unit's are generally used for broadcast purposes. Especially since utilizing a RMS limiter won't catch the peaks even when utilizing it as a peak limiter. So that's a little confusing to some. It's more applicable in that way in a recording environment than a broadcast environment.

    You're just going to peak me up just to let me down
    Ms. Remy Ann David
     
  5. Boswell

    Boswell Moderator Distinguished Member

    Think of r.m.s. power as being the heating effect you would get if your power amp fed an electric bar heater instead of a loudspeaker. Standing in front of the heater, you would be sensitive to changes in the heat output on a timescale of (say) tens of seconds, but you would not notice a short large peak or a gap lasting less than a second.

    R.m.s. and peak measures tell you very different things about the audio signal.
     
  6. Alécio Costa - Brazil

    Alécio Costa - Brazil Well-Known Member

    A bit of electrical engineering theory

    V(t) = 311.sen w.t

    311 is the peak signal (Volts)
    W = 2 x Pi x F
    Pi = 3.141592..
    F = 60Hz (typically)

    If you divide 311 for SQR 2 = 219.91 Volts >>220 Volts
    (Voltage in Brazil, some parts of Europe, Japan)

    311 is the peak while 220 is the "mean value" your devices need to receive from your local energy supplier.


    In the USA:

    V(t) = 155.56 sen w.t

    155.56 divided for SQr 2 = 110 Volts
     
  7. djmukilteo

    djmukilteo Well-Known Member

    http://en.wikipedia.org/wiki/Root_mean_square

    not sure what you were calculating there
    but this might help elaborate
     

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